A fuel injector for a compression ignition engine includes a nozzle defining a plurality of holes through which fuel is injected into a combustion chamber at high pressure. The holes are typically microscopic, often less than 300 micrometers in diameter. Accordingly, even if the holes are visible, ascertaining the quantity of holes, the angular orientation of the holes, and the sizes of the holes is difficult, if not impossible, to perform visually, especially in high-volume commercial operations such as nozzle manufacturing or remanufacturing.
However, it is desirable to sort nozzles based on their hole configurations. For example, during nozzle manufacturing, it is desirable to ensure that the holes are properly formed prior to installation in an engine, and therefore it is desirable to sort newly manufactured nozzles based on whether the holes are within design specification.
Remanufacturing involves obtaining used nozzles (and other engine components) and reconditioning them for further use. Accordingly, it is desirable to test used nozzles to determine whether the holes are still within design specification and whether any holes have become blocked during use, and to sort the nozzles accordingly. Furthermore, the configuration of the holes, such as the quantity of holes, the angular orientation of the holes, and the size of the holes, determines characteristics of the spray pattern of the fuel as it is injected into a combustion chamber, and therefore the configuration of the holes affects engine performance. Some hole configurations are optimal for certain engines and applications, and are not acceptable for other engines and applications. Accordingly, it is desirable to sort nozzles based on the configuration of the holes. In some circumstances, nozzles having different hole configurations are otherwise identical to one another in all other respects only the configuration of the holes differentiates them.
It is also desirable to sort nozzles during engine servicing. For example, testing the efficacy of a nozzle and its holes may determine whether a blocked nozzle hole is the cause of a perceived engine operating problem.
Testing the efficacy and spray pattern of a fuel injector nozzle is presently performed by passing a liquid through the holes of the nozzle and visually observing the spray pattern. For example, Bunch, Jr. et al. describe, in U.S. Pat. No. 5,000,043, an apparatus and method for spraying fuel from a nozzle and observing the subsequent spray pattern. Kojima et al. describe, in U.S. Pat. No. 6,053,037, an apparatus in which liquid is sprayed from the nozzle being tested into a saucer having a plurality of partitions. Sensors measure the head pressure in each of the partitions to determine the amount of the liquid collected therein. Other known testing includes a determination of mass flow rate out of the injector at a predetermined injection pressure.
Prior art fuel injector nozzle testing apparatuses and methods thus require fuel or other liquid to be passed through the holes of a nozzle, which requires a hydraulic circuit to provide the fuel or other liquid to the nozzle. The hydraulic circuit adds cost and mechanical complexity to the testing apparatus, and a substantial amount of time is required to perform the test of each nozzle. Moreover, the method of passing liquid through the holes of a nozzle is not sufficiently refined to enable an observer to differentiate the nozzles being tested on the basis of many variations from nozzle to nozzle.
The present disclosure is directed to one or more of the problems set forth above.